861540091 has 4 divisors (see below), whose sum is σ = 891248400. Its totient is φ = 831831784.

The previous prime is 861540089. The next prime is 861540103. The reversal of 861540091 is 190045168.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 861540091 - 2¹ = 861540089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (861540391) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14854111 + ... + 14854168.

It is an arithmetic number, because the mean of its divisors is an integer number (222812100).

Almost surely, 2^861540091 is an apocalyptic number.

861540091 is a deficient number, since it is larger than the sum of its proper divisors (29708309).

861540091 is a wasteful number, since it uses less digits than its factorization.

861540091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29708308.

The product of its (nonzero) digits is 8640, while the sum is 34.

The square root of 861540091 is about 29352.0031854727. The cubic root of 861540091 is about 951.5358687102.

The spelling of 861540091 in words is "eight hundred sixty-one million, five hundred forty thousand, ninety-one".